The Billfish (Istiopherinae): The Billfish Istiopherinae sub-family are members of the Xiphiidae Family that includes the billfishes, marlins, sailfishes, and swordfishes, all large, oceanic, pelagic surface fish found in all tropic and semitropical waters of the Indian and Pacific Oceans.

The Xiphiidae are characterized by their long, well-compressed bodies, small teeth, and long bills which they use as spears to attack and stun their prey. The first dorsal fin of these fish generally has a tall front lobe, and a long base that is quite low at mid-body; the first dorsal fin base ends near the origin of the second dorsal fin. The Xiphiidae have two keels on each side of the tail base.

Globally there are six species of Istiopherinae known and all six are found in Mexican waters: Striped Marlin, Blue Marlin, Black Marlin, Sailfish, Broadbill Swordfish, and Shortbilled Spearfish.